In conventional elevators, if, for some reason, a car is moved further upward than a normal hoisting zone, a counterweight moves below the normal hoisting zone. Then, the counterweight collides with a counterweight buffer installed in a hoistway floor portion. Thus, mechanical shock from the collision of the counterweight with the hoistway floor portion is buffered, and rising of the car is stopped.
However, if the counterweight collides with the counterweight buffer at a faster speed than a design velocity, the mechanical shock from the collision may not be buffered sufficiently. Thus, methods have been proposed in which safeties for making the counterweight perform an emergency stop when the descent speed of the counterweight (ascent speed of the car) reaches a preset speed are mounted to the counterweight. However, in such methods, it is necessary for space to be secured for installing a speed governor for detecting the speed of the counterweight, and for the safeties for the counterweight, etc., increasing the overall size and expense of the elevator.
Braking apparatuses for stopping the car and the counterweight by gripping a main rope suspending the car and the counterweight have also been proposed, but in braking apparatuses of this type, mechanisms for generating a braking force are large, and constructions for releasing the braking force are complicated, making the machinery expensive.